Abstract : Humans speak to dogs using a special speech register called Pet-Directed Speech (PDS) which is very similar to Infant-Directed Speech (IDS) used by parents when talking to young infants. These two type of speech share prosodic features that are distinct from the typical Adult-Directed Speech (ADS): a high pitched voice and an increased pitch variation. So far, only one study has investigated the effect of PDS on dogs' attention. We video recorded 44 adult pet dogs and 19 puppies when listening to the same phrase enounced either in ADS or in PDS or in IDS. The phrases were previously recorded and were broadcasted via a loudspeaker placed in front of the dog. The total gaze duration of the dogs toward the loudspeaker, was used as a proxy of attention. Results show that adult dogs are significantly more attentive to PDS than to ADS and that their attention significantly increases along with the rise of the fundamental frequency of human' speech. It is likely that the exaggerated prosody of PDS is used by owners as an ostensive cue for dogs that facilitates the effectiveness of their communication, and should represent an evolutionarily determined adaptation that benefits the regulation and maintenance of their relationships. Humans speak to dogs using a special speech register called pet-directed speech (PDS) 1–4 , which is very similar to infant-directed speech (IDS) used by parents when talking to young infants. These two types of speech share prosodic and syntactic features that are distinct from the typical adult-directed speech (ADS): a high pitched voice, an increased pitch variation, short utterances, a reduced syntactic and semantic complexity, and word repetitions 1–5. PDS and IDS are also commonly described as 'happy voices' , in comparison to ADS presenting a relatively inhibited emotional content 6. Both speeches have been shown to vary according to the interaction context 7–9 , for instance PDS' prosodic features are enhanced in a positive reunion situation 9. Several studies suggest that IDS is used by humans in order to modulate infants' attention and state of arousal and to communicate their positive affect and intentions in a non-verbal way 10–14. IDS may also facilitate the emergence of language in infants by emphasizing the linguistic structure 15, 16 , for instance by using hyperaticulation of vowels 2, 3, 17 , or words repetition 18. Authors highlighted these functions in studying babies' preference for IDS toward ADS 19, 20 : infants have a longer fixation on, or turn more often the head toward visual targets that produced IDS 19. Infants also better remember and look longer at adults who have addressed them with IDS 20 , and this preference is present when IDS is produced by the infants' own mother as well as by an unfamiliar mother 12, 20. In addition, the exaggerated acoustic features of IDS elicit increased neural activity in infants, related to atten-tional processing 21. Infants also present increased social and affective responsiveness while listening to IDS compared to ADS 19. PDS and IDS may be similar because both infants and dogs are non-verbal listeners and because the affective bond between owners and dogs mirrors the human parents-infant bond. Indeed, both owners and dogs experience an important secretion of oxytocin after a brief period of cuddling 22 and a study highlighted common brain activation when mothers viewed images of both their child and dog 23. In the context of human-dog communication, there is evidence that dogs present an increased neuronal activity in the auditory cortex when listening to vocalizations with positive emotional valence compared to negative or neutral emotional valence 24. Moreover, after a greeting involving eye contact and a high pitched voice, dogs are more likely to follow the humans gaze, similarly to young children do 25, 26. Similarly, dogs are more motivated to answer a command to find hidden food in high-pitched informative than in low-pitched imperative trials 27 , suggesting that they are sensitive to the nonverbal quality of human vocal signals.